"Dave" wrote in message
. ..
Big Nose wrote:

If a transceiver has an in built automatic antenna tuning and matching
unit, is there any point in measuring the VSWR as a way of ascertaining
its performance?

NOPE! The VSWR in the line = The VSWR in the line = The VSWR in the
line = The VSWR in the line. The internal tuner does absolutely nothing
[NOTHING] to the VSWR in the line.

The internal tuner will make the radio 'happy' within it's tuning range,
but it does NOTHING about the VSWR in the line!



Obviously this would be measured with a thru line meter which would be
placed in the feeder system. However, I have been thinking and it
would appear that the tuning and matching unit would become part of the
antennas impedance (its late and I hope that makes sense).

The reason I ask is because I am trying to find out how well certain
transceivers will perform with antennas which are designed for
different systems.



Agree.

But, whether you're doing your testing or operating afterward, there's
usually some value in knowing the VSWR in the line. It may only serve to
clue you to a problem -- and that's info worth having. I'm depending on the
slightly risky assumption that most tuners you test will be able to match to
a less-than-ideal antenna system with high VSWR in the feedline -- one
that's not putting much power into the air.

I had a USN antenna experience with an improperly-modified shipboard HF XMIT
antenna. The Radiomen said it was hard to
tune to it, the reflected power was always high and they never seemed able
to "get out on it" (meaning poor reception reports from the distant end).

When we put the antenna right, all their problems went away.